3 ms·

The melting of silicon was a common phenomenon already during the second breakdown of power transistors, e.g. in audio amplifiers or in TV sets, more than a hal

The melting of silicon was a common phenomenon already during the second breakdown of power transistors, e.g. in audio amplifiers or in TV sets, more than a half of century ago. In semiconductors there is a positive feedback between temperature and the current that passes through them, so once a certain threshold is passed, the current and the temperature grow very quickly until the semiconductor is melted. This is opposite to the behavior of metals, where resistance grows with temperature, tending to limit the current that passes through the metal, when it overheats. The currents through the transistors of SOTA logic gates are very small, but their volumes are also very small, so the power density is similar to that in high power transistors. Thus thermal breakdown that leads to silicon melting is easily achievable. This is why any modern CPU has on-die temperature sensors, so that temperature is monitored and power dissipation is limited, to ensure that the threshold that triggers positive thermal feedback is never reached.

flossEveryday 4mo ago
wow, i had heard of transistor thermal runaway, but i didn't know you could reach silicon melting point temperatures. though i guess in hindsight it makes sense that, considering that during the manufacturing process semiconductors are already exposed to very high temperatures, if you are instantly permanently altering a device with heat (as you do when you destroy it through thermal runaway), you must be reaching comparably high temperatures. what type of people look at heat transfer at the device level in an IC (and at such short time scales)? where can i learn more about that? this looks like it could have an impact in analog power circuits, because even if you don't destroy the transistor you could alter its characteristics, but i haven't seen a lot of attention being paid to that. personally i guess i figured individual transistors never went significantly beyond the temperature ranges we already consider for the circuit as a whole. thank you for sharing

flossEveryday 4mo ago

wow, i had heard of transistor thermal runaway, but i didn't know you could reach silicon melting point temperatures. though i guess in hindsight it makes sense that, considering that during the manufacturing process semiconductors are already exposed to very high temperatures, if you are instantly permanently altering a device with heat (as you do when you destroy it through thermal runaway), you must be reaching comparably high temperatures. what type of people look at heat transfer at the device level in an IC (and at such short time scales)? where can i learn more about that? this looks like it could have an impact in analog power circuits, because even if you don't destroy the transistor you could alter its characteristics, but i haven't seen a lot of attention being paid to that. personally i guess i figured individual transistors never went significantly beyond the temperature ranges we already consider for the circuit as a whole. thank you for sharing